The present invention is directed to a method for the implementation of a fault diagnostic system having a number of diagnostic modules that monitor sub-systems, and to an in-vehicle fault diagnostic system.
Electronic control devices for controlling and regulating systems frequently comprise diagnostic modules for recognizing faults in the controlled or regulated system. The diagnostic results can, for example, result in a deactivation of sub-systems, a drive of alarm displays or an entry into a fault memory for documentation purposes. Such control devices are utilized particularly often in motor vehicles.
In a networked system, an outage of an individual component or of a sub-system can deteriorate the correct function of other components or sub-systems. When such cross-dependencies are not taken into consideration in a system of diagnostic modules, this, in addition to leading to the entry of the causative fault, leads to further entries of successor faults into a fault memory. Such successor faults can, under certain circumstances, characterize correctly operating sub-systems or components as being faulty.
In order to avoid the entry of successor faults into the fault memory, a cross-interlock of functions can ensue. It must thereby be assured that the causative fault is recognized before the successor fault. This is achieved in that diagnostic modules that are dependent on one another are started in a specific sequence, so that a diagnostic module whose diagnostic result is dependent on the result of the fault diagnosis of a different diagnostic module is not started until after the arrival of the corresponding diagnostic result.
German Patent Application No. 40 40 927 discloses fault storing in a control means of a motor vehicle, whereby a fault sequence is deposited in a fault sequence memory in the sequence of the occurrence of the faults. Whether the fault is present at the moment is identified in a fault register memory for each fault of the fault sequence memory, being identified by a fault identification flag. An entry into the fault sequence memory only ensues when the pertaining fault identification flag is not set for an occurring fault.
SAE Technical Paper Series 980512, xe2x80x9cA New Object-Oriented Diagnostic System Management for Power-Train Control Units with ODBxe2x80x9d, presents an in-vehicle (on-board) diagnostic system that comprises a set of central modules for handling cross-connections. Due to the introduction of central modules for a fault handling, a better configuration of the system is achieved compared to local cross-interlocks of diagnostic functions. The central modules assume the job of a central administration and coordination of error statuses that are reported by the diagnostic functions.
An object of the present invention is to offer a method for the implementation of a fault diagnostic system and a fault diagnostic system having a number of diagnostic modules, whereby the sequence of the fault messages arriving from the diagnostic modules need not be taken into consideration.
This object is achieved in accordance with the invention in a method for implementing a fault diagnostic system having a number of diagnostic modules that monitor sub-systems during a diagnostic cycle and provide a diagnostic result and in an in-vehicle fault diagnostic system operating according to the method.
In an embodiment, a diagnostic cycle of a second diagnostic module is started without waiting for a diagnostic result of a first diagnostic module, the second diagnostic module having a diagnostic result dependent on a result of a fault diagnosis of at least one first diagnostic module. The diagnostic result of the second diagnostic module is written into a secondary fault memory when the diagnostic result of the first diagnostic module is not yet provided after an end of the diagnostic cycle of the second diagnostic module. The diagnostic result of the second diagnostic module is written into a primary fault memory when the first diagnostic module has not diagnosed a fault after an end of a diagnostic cycle of the first diagnostic module, the primary fault memory having entries for judging functionability of the sub-systems.
The distinction between a primary and a secondary fault memory makes it possible to classify a diagnostic result as preliminary. When all boundary conditions are met, particularly when all diagnostic results are present from which the diagnostic result of the pertaining diagnostic module depends, the diagnostic result classified as preliminary can be classified as final. A diagnostic module dependent on the result of another diagnostic module need therefore not necessarily wait for the arrival of the pending diagnostic result but can already start its diagnostic cycle. This is of particular advantage when the diagnostic modules must process comparatively time-consuming routines or when a diagnostic module is dependent on the diagnostic result of a chain of diagnostic modules.
When it is found that the preliminary diagnostic result is based on values that were considered faulty by another diagnostic module, then the dependent diagnostic result is preferably deleted from the secondary fault memory.
In one embodiment of the invention, the diagnostic result of a second diagnostic module that is dependent on the diagnostic result of a first diagnostic module is also written into the fault memory when the first diagnostic module has terminated its diagnostic cycle before the second diagnostic module and has not recognized any fault. The decision as to whether a diagnostic result is transferred from the secondary fault memory into the primary fault memory can then be made by a central diagnostic module. As a result thereof, the configuration of the fault diagnostic system is simplified.
In an embodiment, dependencies between diagnostic modules are stored in a table or matrix (cross-interlock matrix). A diagnostic module or a central diagnostic module can derive from this matrix whether a diagnostic result is to be interpreted as preliminary or final. Accordingly, the diagnostic result is then entered into the primary fault memory or into the secondary fault memory.
Although the invention can be utilized both in vehicles and production systems as well as in combination with any system to be monitored, the preferred area of employment is the fault diagnosis of sub-systems of a motor vehicle. For example, this can thereby be a matter of a fault diagnosis in conjunction with a motor control device, a power train control, an electromechanical braking system, an electromagnetic valve control or the like.
These and other features of the invention(s) will become clearer with reference to the following detailed description of the presently preferred embodiments and accompanied drawings.